The present invention relates to a polishing composition used, for example, in polishing for forming conductor wiring for a semiconductor device, and to a polishing method using such a polishing composition.
Currently, a damascene process wherein a chemical mechanical polishing (CMP) technology is used has become the main method for forming conductor wiring for a semiconductor device. When the conductor wiring is formed, first of all, a trench is formed on an insulator layer provided on a semiconductor substrate, and then a barrier layer comprising titanium or titanium nitride is formed on the insulator layer. Subsequently, a conductor layer is formed on the barrier layer such that at least the trench is filled with the conductor layer, and then a portion of the conductor layer and a portion of the barrier layer, each of which is positioned outside the trench, are removed by chemical mechanical polishing, whereby a portion of the conductor layer, which is left on the insulator layer, positioned inside the trench functions as the conductor wiring.
Japanese National Phase Laid-Open Patent Publication No. 2000-501771, Japanese Laid-Open Patent Publication Nos. 10-67986, 10-265766 and 11-116948 disclose a conventional polishing composition used in polishing for removing a portion of a conductor layer and a portion of a barrier layer, each of which is positioned outside a trench. However, conventional polishing compositions do not have the ability to polish a barrier layer comprising titanium at a high stock removal rate Furthermore, conventional polishing compositions have the problem of reduction in safety due to the addition of fluoride and the problem of metallic contamination of the semiconductor device due to the addition of a metallic catalyst.
The polishing for removing the portion of the conductor layer and the portion of the barrier layer, each of which is positioned outside the trench, may be carried out with two or more types of polishing compositions. More specifically, polishing compositions different from each other may be used in the steps of: removing a part of the portion of the conductor layer positioned outside the trench in order to expose the upper surface of the barrier layer, and removing the residual of the portion of the conductor layer positioned outside the trench and the portion of the barrier layer positioned outside the trench in order to expose the upper surface of an insulator layer. However, the above method requires a lot of work to provide the two or more types of polishing compositions, and a lot of work to replace the polishing compositions, whereby working efficiency is decreased.